Many surgical procedures require or involve the use of internal tethering of damaged bone or other tissue in order to fix the bone or tissue in position in order to address a misalignment, instability, and/or to enable the healing process to progress, for example allowing bone or tendon regrowth at a damage area. In order to facilitate such tethering it is often necessary to employ some form of bone or tissue anchor or similar fixation device which serves as a fixed point to which a suture may be anchored, in order to allow a tendon or ligament to be suture and thus secured to the bone. Fixation devices may also be use to enable additional surgical apparatus to be secured as required.
Such fixation devices may take many forms, for example an externally threaded bone screw, pin, plate or other, which may be threaded into a suitable hole formed in a section of bone, and which will therefore, once located, secure a suture to the bone which may then be utilised to achieve fixation of tendons or ligaments to the respective bone, for example when performing a rotator cuff repair or the like.
Commercially produced surgical fixation tools such as screws, pins, anchors, etc. are typically injection moulded from a suitable material such as a polymer or the like. These injection moulded parts can be manufactured from a single resin or a polymer mix, which is typically in the form of resin combined with a growth promoting medium, for example tricalciumphosphate (TCP) or any other suitable alternative. These mixes may vary in composition, for example containing 80% polymer to 20% growth promoting medium. When a mix of polymer and growth promoting medium is injected into the tool cavity in order to mould the fixation tool it is virtually impossible to control the distribution of growth promoting medium and as a result it is randomly spread throughout the cavity. Growth promoting medium that resides sub-surface of the final moulded product is effectively locked in by the surrounding polymer resin and is not readily available to be decalcified in order to promote bone ingrowth and/or bone regrowth once the fixation tool has been implanted.
It is therefore an object of the present invention to provide a tissue-integration device and a method of manufacturing same, which addresses some of the above mentioned problems of the prior art.